It is normal to not receive 100% packet reply when pinging ip phone. This is because the IP phones have been designed to only reply to an echo every 10ms, in order to withstand Denial of Service (DoS) attacks. A Cisco IOS gateway sends echos more frequently so one out of two will timeout. This is not the case for a PC since the time between two echos is greater than 10ms.
For troubleshooting icluding pinging Default gateway, ping own IP address and ping 127.0.0.1.
